The present invention relates to a coil for a sputter deposition machine for processing semiconductor substrates and, more particularly, to an improved coil for an ionized metal plasma physical vapor deposition machine.
Typically, an IMP PVD (ionized metal plasma physical vapor deposition) machine is provided with an RF (radio frequency) coil in the chamber thereof for the purpose of emitting RF energy within the area of the coil. The purpose of the RF energy is to ionize copper atoms as they are emitted from a copper source target during deposition. The ionized copper atoms are then accelerated towards the surface of the silicon wafer.
Typically, the plasma coils are made of pure copper. Pure copper is a relatively soft material so that when high power above about two kilowatts is applied to a plasma coil in a conventional IMP Cu PVD system, the Cu coil heats up and is susceptible to sagging or other mechanical deformation. The sagging or other deformation can lead to problems ranging from non-uniformities in the deposition, to reduced chamber part life to, more severely, shorting of the coil with other chamber parts. Coil failure can take several forms. Even slight mechanical deformation by sagging, twisting, buckling or other means can cause the deposition process, specifically the uniformity of the layer deposited on the silicon wafer, to drift out of specification. In a production environment, maintaining process parameters such as film uniformity is critical.
Greater mechanical deformation of the coil caused by overheating could cause the coil to short with the chamber shields, which are the closest chamber part.
Accordingly, there is a need for an improved strength coil for use in IMP copper deposition.